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A074315
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Abundant triangular numbers.
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1
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36, 66, 78, 120, 210, 276, 300, 378, 528, 630, 666, 780, 820, 990, 1128, 1176, 1326, 1540, 1596, 1770, 1830, 2016, 2080, 2346, 2556, 2628, 2850, 3160, 3240, 3486, 3570, 3828, 4095, 4278, 4560, 4656, 4950, 5460, 5778, 5886, 6216, 6328, 6786, 7140, 7260
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OFFSET
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1,1
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LINKS
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FORMULA
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EXAMPLE
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a(2)=66 because sum of aliquot divisors of 66 (which is a triangular number) is 1+2+3+6+11+22+33=78 which is more than 66, hence it is abundant. 66 is 2nd abundant triangular number.
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MATHEMATICA
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Select[Accumulate[Range[150]], Total[Divisors[#]]>2#&] (* Harvey P. Dale, Dec 18 2014 *)
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PROG
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(PARI) listA074315(m) = {for (i=1, m, t = i*(i+1)/2; if (sigma(t) > 2*t, print1(t, ", ")); ); } \\ up to the m-th triangular number; Michel Marcus, Mar 10 2013
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CROSSREFS
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KEYWORD
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base,nonn
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AUTHOR
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STATUS
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approved
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